Photoelectric conversion apparatus having filler member and airgap arranged in interior of trench portion, photoelectric conversion system, and moving body

ABSTRACT

A photoelectric conversion apparatus includes a plurality of photoelectric conversion circuits configured to be arranged in a semiconductor layer having a first plane and a second plane. The plurality of photoelectric conversion circuits is individually isolated by an isolation structure. The semiconductor layer includes a plurality of trench portions arranged on the first plane of each of the photoelectric conversion circuits. The plurality of trench portions is configured of a first trench portion extending in a first direction as an in-plane direction of the first plane and a second trench portion extending in a second direction as an in-plane direction of the first plane intersecting with the first direction. A filler member and an airgap are arranged in an interior of a trench portion at a position where the first trench portion and the second trench portion intersect with each other.

BACKGROUND Technical Field

One disclosed aspect of the embodiments relates to a photoelectricconversion apparatus and a photoelectric conversion system.

Description of the Related Art

There is provided a photoelectric conversion apparatus which improvesquantum efficiency by increasing a light path length of light incidenton a photoelectric conversion element by refracting the incident lightthrough a concavo-convex structure arranged on a light receiving planeof the photoelectric conversion element.

However, in Japanese Patent Application Laid-Open No. 2018-093234, thereis an issue in that considerable optical color mixture occurs because oflimitation in an increase amount of the optical path length.

SUMMARY

One aspect of the embodiments is directed to a photoelectric conversionapparatus and a photoelectric conversion system capable of reducing theoptical color mixture.

According to an aspect of the disclosure, a photoelectric conversionapparatus includes a plurality of photoelectric conversion circuitsconfigured to be arranged in a semiconductor layer having a first planeand a second plane opposite to the first plane. The plurality ofphotoelectric conversion circuits is individually isolated by anisolation structure. The semiconductor layer includes a plurality oftrench portions arranged on the first plane of each of the photoelectricconversion circuits demarcated by the isolation structure. The pluralityof trench portions is configured of a first trench portion extending ina first direction as an in-plane direction of the first plane and asecond trench portion extending in a second direction as an in-planedirection of the first plane intersecting with the first direction. Afiller member and an airgap are arranged in an interior of a trenchportion at a position where the first trench portion and the secondtrench portion intersect with each other.

Further features of the disclosure will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a photoelectric conversionapparatus according to a present exemplary embodiment.

FIG. 2 is a schematic diagram illustrating a photodiode (PD) substrateof the photoelectric conversion apparatus according to the presentexemplary embodiment.

FIG. 3 is a schematic diagram illustrating a circuit substrate of thephotoelectric conversion apparatus according to the present exemplaryembodiment.

FIG. 4 is a diagram illustrating an example of a pixel circuitconfiguration of the photoelectric conversion apparatus according to thepresent exemplary embodiment.

FIGS. 5A to 5C are diagrams schematically illustrating a drivingconfiguration of the pixel circuit of the photoelectric conversionapparatus according to the present exemplary embodiment.

FIG. 6 is a cross-sectional diagram illustrating a pixel of thephotoelectric conversion apparatus according to a first exemplaryembodiment.

FIG. 7 is a diagram illustrating a plan view of the pixel of thephotoelectric conversion apparatus according to the first exemplaryembodiment.

FIG. 8 is a schematic diagram of the photoelectric conversion apparatusaccording to the first exemplary embodiment.

FIG. 9 is a schematic diagram of the photoelectric conversion apparatusaccording to the first exemplary embodiment.

FIGS. 10A and 10B are schematic diagrams of the photoelectric conversionapparatus according to the first exemplary embodiment.

FIG. 11 is a schematic diagram of a photoelectric conversion apparatusaccording to a second exemplary embodiment.

FIG. 12 is a schematic diagram of a photoelectric conversion apparatusaccording to a third exemplary embodiment.

FIG. 13 is a functional block diagram of a photoelectric conversionsystem according to a fourth exemplary embodiment.

FIGS. 14A and 14B are functional block diagrams of a photoelectricconversion system according to a fifth exemplary embodiment.

FIG. 15 is a functional block diagram of a photoelectric conversionsystem according to a sixth exemplary embodiment.

FIG. 16 is a functional block diagram of a photoelectric conversionsystem according to a seventh exemplary embodiment.

FIGS. 17 and 17B are functional block diagrams of a photoelectricconversion system according to an eighth exemplary embodiment.

DESCRIPTION OF THE EMBODIMENTS

The embodiments described hereinafter are merely the examples embodyingthe technical sprit of the disclosure, and are not intended to limit thedisclosure. In order to provide clear descriptions, in the drawings,sizes and a positional relationship of members may be illustrated withexaggeration. In the below-described exemplary embodiments, the samereference numerals are applied to constituent elements similar to eachother, and descriptions thereof will be omitted. In the following, theterm “unit” may refer to a software context, a hardware context, or acombination of software and hardware contexts. In the software context,the term “unit” refers to a functionality, an application, a softwaremodule, a function, a routine, a set of instructions, or a program thatcan be executed by a programmable processor such as a microprocessor, acentral processing unit (CPU), or a specially designed programmabledevice or controller. A memory contains instructions or program that,when executed by the CPU, cause the CPU to perform operationscorresponding to units or functions. In the hardware context, the term“unit” refers to a hardware element, a circuit, an assembly, a physicalstructure, a system, a module, or a subsystem. It may includemechanical, optical, or electrical components, or any combination ofthem. It may include active (e.g., transistors) or passive (e.g.,capacitor) components. It may include semiconductor devices having asubstrate and other layers of materials having various concentrations ofconductivity. It may include a CPU or a programmable processor that canexecute a program stored in a memory to perform specified functions. Itmay include logic elements (e.g., AND, OR) implemented by transistorcircuits or any other switching circuits. In the combination of softwareand hardware contexts, the term “unit” or “circuit” refers to anycombination of the software and hardware contexts as described above. Inaddition, the term “element,” “assembly,” “component,” or “device” mayalso refer to “circuit” with or without integration with packagingmaterials. Furthermore, depending on the context, the term “portion,”“part,” “device,” “switch,” or similar terms may refer to a circuit or agroup of circuits. The circuit or group of circuits may includeelectronic, mechanical, or optical elements such as capacitors, diodes,or transistors. For example, a switch is a circuit that turns on andturns off a connection. It can be implemented by a transistor circuit orsimilar electronic devices.

Hereinafter, exemplary embodiments of the disclosure will be describedin detail with reference to the appended drawings. In thebelow-described exemplary embodiments, wordings (e.g., “up”, “down”,“right”, and “left”, and other wordings including these wordings) whichexpress a particular direction and positions are used as necessary.These wordings are used for the sake of simplicity and easyunderstanding of the exemplary embodiments described with reference tothe appended drawings, and meanings of these wordings should not beconstrued as limiting the technical range of the disclosure.

In this specification documents, a planar view refers to a view seenfrom a direction perpendicular to a light incident plane of asemiconductor layer. Further, a cross-sectional plane refers to a planeperpendicular to the light incident plane of the semiconductor layer. Ina case where the light incident plane of the semiconductor layer has arough surface in a microscopic view, the planar view is defined bytaking the light incident plane of the semiconductor layer in amacroscopic view as a reference.

In the below-described exemplary embodiments, a potential of an anode ofan avalanche photodiode (APD) is fixed, and a signal is taken from acathode thereof. Accordingly, a first conductivity type semiconductorregion, in which a majority carrier is an electric charge of a polaritythe same as a polarity of a signal charge, refers to an N-typesemiconductor region, and a second conductivity type semiconductorregion, in which a majority carrier is an electric charge of a polaritydifferent from the polarity of the signal charge, refers to a P-typesemiconductor region.

In addition, the disclosure can also be realized in a case where apotential of a cathode of the APD is a fixed potential, and a signal istaken from an anode thereof. In this case, a first conductivity typesemiconductor region, in which a majority carrier is an electric chargeof a polarity the same as a polarity of a signal charge, refers to aP-type semiconductor region, and a second conductivity typesemiconductor region, in which a majority carrier is an electric chargeof a polarity different from the polarity of the signal charge, refersto an N-type semiconductor region. Although each of the exemplaryembodiments will be described with respect to a case where a potentialof one of the nodes of the APD is fixed, potentials of both nodes may befluctuated.

In a case where a wording “impurity concentration” is simply used inthis specification documents, this wording is used to mean a netimpurity concentration obtained by subtracting impurities compensated byreverse conductivity-type impurities. In other words, “impurityconcentration” indicates a net doping concentration. A semiconductorregion where a P-type additive impurity concentration is higher than anN-type additive impurity concentration is a P-type semiconductor region.On the other hand, a semiconductor region where the N-type additiveimpurity concentration is higher than the P-type additive impurityconcentration is an N-type semiconductor region.

A photoelectric conversion apparatus and a driving method thereofaccording to the disclosure, which are common to each of the exemplaryembodiments, will be described with reference to FIG. 1 to FIGS. 5A to5C.

FIG. 1 is a diagram illustrating a multilayer-type photoelectricconversion apparatus 100 according to the present exemplary embodiment.

The photoelectric conversion apparatus 100 is configured of twosubstrates, i.e., a sensor substrate 11 and a circuit substrate 21,which are stacked one on top of another and electrically connected toeach other. The sensor substrate 11 includes a first semiconductor layerincluding photoelectric conversion elements 102 described below and afirst wiring structure. The circuit substrate 21 includes a secondsemiconductor layer including a circuit of a signal processing unit 103described below and a second wiring structure. The photoelectricconversion apparatus 100 is configured of the second semiconductorlayer, the second wiring structure, the first wiring structure, and thefirst semiconductor stacked in that order. The photoelectric conversionapparatus 100 described in each of the exemplary embodiments is aback-face illumination type photoelectric conversion apparatus having afirst plane on which light is incident and a second plane on which acircuit substrate is arranged.

Hereinafter, although the sensor substrate 11 and the circuit substrate21 formed of diced chips are described, types of the substrates 11 and21 are not limited to diced chips. For example, the respectivesubstrates 11 and 21 may be formed of wafers. Further, the substrates 11and 21 may be diced after being laminated in a state of wafers, or maybe laminated and joined together after being formed into diced chips.

A pixel region 12 is arranged on the sensor substrate 11, and a circuitregion 22 for processing a signal detected from the pixel region 12 isarranged on the circuit substrate 21.

FIG. 2 is a diagram illustrating an arrangement example of the sensorsubstrate 11. Pixels 101, each of which includes a photoelectricconversion element 102 including an APD, are arrayed in atwo-dimensional array state in a planar view to form the pixel region12.

Typically, the pixels 101 are pixels for forming an image. However, animage does not have to be formed thereby when the pixels 101 are usedfor a time-of-flight (TOF) system. In other words, the pixels 101 may beused for measuring an arrival time of light and an amount of light.

FIG. 3 is a diagram illustrating a structure of the circuit substrate21. The circuit substrate 21 includes signal processing units orcircuits 103 for processing electric charges photoelectrically convertedby the photoelectric conversion elements 102 in FIG. 2, a column circuit112, a control pulse generation unit or circuit 115, a horizontalscanning circuit unit 111, a signal line 113, and a vertical scanningcircuit unit 110.

The photoelectric conversion elements 102 in FIG. 2 and the signalprocessing units 103 in FIG. 3 are electrically connected to each othervia connection wiring arranged for each of the pixels 101.

The vertical scanning circuit unit 110 receives a control pulse suppliedfrom the control pulse generation unit 115 and supplies the controlpulse to each of the pixels 101. A logic circuit such as a shiftregister or an address decoder is used for the vertical scanning circuitunit 110.

Signals output from the photoelectric conversion elements 102 of thepixels 101 are processed by the signal processing units 103. Each of thesignal processing units 103 includes a counter and a memory, and adigital value is stored in the memory.

In order to read out a digital signal stored in the memory of each ofthe pixels 101, the horizontal scanning circuit unit 111 outputs acontrol pulse for sequentially selecting each column to the signalprocessing unit 103.

A signal is output to the signal line 113 from the signal processingunit 103 of the pixel 101 selected by the vertical scanning circuit unit110 in the selected column.

A signal output to the signal line 113 is output to a recording unit orcircuit on the outside of the photoelectric conversion apparatus 100 viaan output circuit 114, or output to the signal processing unit 103.

In FIG. 2 , an array of the photoelectric conversion elements 102 may bearranged in a one-dimensional array state in the pixel region 12.Further, the effect of the present exemplary embodiment can also beacquired with respect to a case of a single pixel. Therefore, thedisclosure also includes the case of a single pixel. A function of thesignal processing unit 103 does not always have to be individuallyprovided to all of the photoelectric conversion elements 102. Therefore,for example, one signal processing unit 103 may be shared by a pluralityof photoelectric conversion elements 102, and the signal processing maybe executed sequentially.

As illustrated in FIGS. 2 and 3 , a plurality of signal processing units103 is arranged in a region overlapping with the pixel region 12 in aplanar view. Then, the vertical scanning circuit unit 110, thehorizontal scanning circuit unit 111, the column circuit 112, the outputcircuit 114, and the control pulse generation unit 115 are arranged in aregion which overlaps with a region between the edge of the sensorsubstrate 11 and the edge of the pixel region 12 in a planar view. Inother words, The sensor substrate 11 includes the pixel region 12 and anon-pixel region arranged in the surroundings of the pixel region 12,and the vertical scanning circuit unit 110, the horizontal scanningcircuit unit 111, the column circuit 112, the output circuit 114, andthe control pulse generation unit 115 are arranged in the regionoverlapping with the non-pixel region in a planar view.

FIG. 4 illustrates an example of a block diagram including an equivalentcircuit in FIGS. 2 and 3 .

In FIG. 2 , the photoelectric conversion elements 102 including the APDs201 are arranged on the sensor substrate 11, and the other members arearranged on the circuit substrate 21.

Each of the APDs 201 is a photoelectric conversion unit which executesphotoelectric conversion to generate an electric charge pair dependingon incident light.

A voltage VL (first voltage) is supplied to an anode of the APD 201. Avoltage VH (second voltage) higher than the voltage VL supplied to theanode is supplied to a cathode of the APD 201. A reverse bias voltagewhich causes the APD 201 to perform avalanche multiplication is suppliedto the anode and the cathode. In a state where the above-describedvoltage is supplied thereto, avalanche multiplication occurs in theelectric charge generated from incident light, so that avalanche currentis generated.

In addition, in a case where reverse bias voltage is supplied thereto,the APD 201 can be operated in the Geiger mode or a linear mode. In theGeiger mode, the APD 201 is operated in a state where a difference inelectric potentials of the anode and the cathode is greater than abreakdown voltage. In the linear mode, the APD 201 is operated in astate where a difference in electric potentials of the anode and thecathode is close to the breakdown voltage, or equal to or less than thebreakdown voltage.

An APD operated in the Geiger mode is called a single-photon avalanchediode (SPAD). For example, the voltage VL (first voltage) of −30V andthe voltage VH (second voltage) of 1V are supplied thereto. The APD 201can be operated in either the linear mode or the Geiger mode. However,it is preferable that the APD 201 be operated as the SPAD because anelectric potential difference is greater than that of the APD 201operated in the linear mode, so that a notable effect can be acquiredwith respect to the withstand voltage.

A quench element 202 is connected to a power source for supplying thevoltage VH and the APD 201. When signal multiplication occurs because ofavalanche multiplication, the quench element 202 functions as a loadcircuit (quench circuit) to suppress avalanche multiplication bysuppressing voltage supplied to the APD 201 (i.e., quench operation).Further, the quench element 202 functions to bring back the voltagesupplied to the APD 201 to the voltage VH by applying electric currentcorresponding to the voltage dropped by the quench operation (i.e.,recharge operation).

The signal processing unit 103 includes a waveform shaping unit orcircuit 210, a counter circuit 211, and a selection circuit 212. In thisspecification documents, the signal processing unit 103 may include anyone of the waveform shaping unit 210, the counter circuit 211, and theselection circuit 212.

The waveform shaping unit 210 shapes a potential change of the cathodeof the APD 201 acquired at the time of photon detection into a pulsesignal and outputs the pulse signal. For example, an inverter circuit isused as the waveform shaping unit 210. In FIG. 4 , an example of theconfiguration using one inverter as the waveform shaping unit 210 isillustrated. However, a circuit including a plurality of inverterconnected in series or another circuit having a waveform shaping effectcan also be used.

The counter circuit 211 counts a pulse signal output from the waveformshaping unit 210 and retains a count value. When a control pulse pRES issupplied thereto via a drive wire 213, a signal retained in the countercircuit 211 is reset.

A control pulse pSEL is supplied to the selection circuit 212 from thevertical scanning circuit unit 110 in FIG. 3 via a drive wire 214 inFIG. 4 (not illustrated in FIG. 3 ), so that the electrical connectionbetween the counter circuit 211 and the signal line 113 is switched onand off. For example, the selection circuit 212 includes a buffercircuit for outputting a signal.

The electrical connection can be switched by arranging a switch such asa transistor between the quench element 202 and the APD 201 or thephotoelectric conversion element 102 and the signal processing unit 103.Similarly, the voltage VH or VL supplied to the photoelectric conversionelement 102 can also be switched electrically by using a switch such asa transistor.

In the present exemplary embodiment, a configuration using the countercircuit 211 is described. However, the photoelectric conversionapparatus 100 may acquire a pulse detection timing by using atime-to-digital converter (TDC) and a memory instead of using thecounter circuit 211. At this time, a generation timing of the pulsesignal output from the waveform shaping unit 210 is converted to adigital signal through the TDC. In order to measure a timing of thepulse signal, a control pulse pREF (reference signal) is supplied to theTDC from the vertical scanning circuit unit 110 in FIG. 1 via a drivewire. By making the control pulse pREF as a reference, the TDC takes aninput timing of a signal output from each of the pixels 101 as arelative time and acquires a signal of that time as a digital signal viathe waveform shaping unit 210.

FIGS. 5A to 5C are diagrams schematically illustrating a relationshipbetween the operation of the APD 201 and the output signal.

FIG. 5A illustrates the APD 201, the quench element 202, and thewaveform shaping unit 210 extracted from FIG. 4 . Herein, an input sideand an output side of the waveform shaping unit 210 are called “node A”and “node B”, respectively. A change of waveform at the node A in FIG.5A is illustrated in FIG. 5B, and a change of waveform at the node B inFIG. 5A is illustrated in FIG. 5C.

In a period between time t0 to time t1, a potential difference of VH-VLis applied to the APD 201 in FIG. 5A. When photons are incident on theAPD 201 at the time t1, avalanche multiplication occurs in the APD 201,and an avalanche multiplication current flows in the quench element 202,so that a voltage of the node A is dropped. When the amount of voltagedrop is further increased, and a difference in electric potentialsapplied to the APD 201 is reduced, the avalanche multiplicationoccurring in the APD 201 is stopped at time t2, so that a voltage of thenode A will not be dropped to lower than a certain level. After that, ina period between the time t2 and the time t3, electric current forcompensating the amount of dropped voltage flows into the node A fromthe voltage VL, so that the electric potential at the node A is settledin the original potential level at time t3. At this time, the outputwaveform which exceeds a certain threshold at the node A is shaped bythe waveform shaping unit 210 and is output as a signal at the node B.

In addition, the arrangement of the signal line 113, the column circuit112, and the output circuit 114 is not limited to the arrangementillustrated in FIG. 3 . For example, the signal line 113 may extend in arow direction, and the column circuit 112 may be arranged at a positionwhere the signal line 113 extends.

The photoelectric conversion apparatus 100 according to each of theexemplary embodiments will be described below.

A photoelectric conversion apparatus 100 according to a first exemplaryembodiment will be described with reference to FIGS. 6 to 12 .

FIG. 6 is a diagram illustrating a cross-sectional view of two pixels101 of photoelectric conversion elements 102 included in thephotoelectric conversion apparatus 100 according to the disclosure,viewed from a direction perpendicular to a plane direction of thesubstrate.

A structure of the photoelectric conversion element 102 will bedescribed. The photoelectric conversion element 102 includes an N-typefirst semiconductor region 311, an N-type fourth semiconductor region314, an N-type sixth semiconductor region 316, and an N-type seventhsemiconductor region 317. The photoelectric conversion element 102further includes a P-type second semiconductor region 312, a P-typethird semiconductor region 313, a P-type fifth semiconductor region 315,and a P-type eighth semiconductor region 318.

In the present exemplary embodiment, as illustrated in thecross-sectional view in FIG. 6 , the N-type first semiconductor region311 is formed in a vicinity of a plane opposite to a light incidentplane, and the N-type seventh semiconductor region 317 is formed in aperiphery of the first semiconductor region 311. The P-type secondsemiconductor region 312 is formed at a position overlapping with thefirst semiconductor region 311 and the seventh semiconductor region 317in a planar view. Further, the N-type fourth semiconductor region 314 isarranged at a position overlapping with the second semiconductor region312 in the planar view, and the N-type sixth semiconductor region 316 isformed in a periphery of the fourth semiconductor region 314.

The N-type impurity concentration is higher in the first semiconductorregion 311 than in the fourth semiconductor region 314 or the seventhsemiconductor region 317. A P-N junction is formed in a region betweenthe P-type second semiconductor region 312 and the N-type firstsemiconductor region 311. However, by making the impurity concentrationin the second semiconductor region 312 be lower than in the firstsemiconductor region 311, all of the second semiconductor region 312becomes a depletion layer region. This depletion layer region furtherextends to part of the first semiconductor region 311, and an intenseelectric field is induced in this extended depletion layer region. Thisintense electric field causes the avalanche multiplication to occur inthe depletion layer region extending to the part of the firstsemiconductor region 311, and the electric current based on theamplified electric charge is output as a signal charge. When lightincident on the photoelectric conversion element 102 isphotoelectrically converted, and avalanche multiplication occurs in thedepletion layer region (i.e., avalanche multiplication region), thegenerated first conductive type electric charges are collected in thefirst semiconductor region 311.

In addition, in FIG. 6 , although sizes of the fourth semiconductorregion 314 and the seventh semiconductor region 317 are approximatelythe same, sizes of the semiconductor regions 314 and 317 are not limitedthereto. For example, the fourth semiconductor region 314 may be formedinto a size larger than a size of the seventh semiconductor region 317,so that the electric charges can be collected in the first semiconductorregion 311 from a wider range.

A concavo-convex structure 325 configured of trench portions is formedon a surface of a semiconductor layer 301 on a side of a light incidentplane. The concavo-convex structure 325 is surrounded by the P-typethird semiconductor region 313, and makes light incident on thephotoelectric conversion element 102 scatter. Because the incident lightobliquely travels through the photoelectric conversion element 102, alight path length greater than a thickness of the semiconductor layer301 can be secured. Therefore, light having a longer wavelength can bephotoelectrically converted in comparison to the case where theconcavo-convex structure 325 is not formed thereon. Furthermore, becausethe concavo-convex structure 325 can prevent incident light from beingreflected within the substrate, an effect of improving the photoelectricconversion rate of incident light can be acquired.

The fourth semiconductor region 314 is formed to overlap with theconcavo-convex structure 325 in the planar view. The area where thefourth semiconductor region 314 overlaps with the concavo-convexstructure 325 in the planar view is greater than the area where thefourth semiconductor region 314 does not overlap with the concavo-convexstructure 325. In comparison to the electric charges generated in aregion close to the avalanche multiplication region, the electriccharges generated in a region far from the avalanche multiplicationregion between the first semiconductor region 311 and the fourthsemiconductor region 314 require longer travel time to reach theavalanche multiplication region. Therefore, there is a possibility thattiming jitter thereof is worsened. By arranging the fourth semiconductorregion 314 and the concavo-convex structure 325 at positions overlappingwith each other in the planar view, an electric field in a deep portionof the photodiode can be enhanced, and time taken to collect theelectric charges generated in a region far from the avalanchemultiplication region can be shortened. Therefore, it is possible toreduce the timing jitter.

Further, by covering the concavo-convex structure 325 with the thirdsemiconductor region 313 three-dimensionally, it is possible to suppressgeneration of thermally excited electric charges at an interfacialsurface of the concavo-convex structure 325. Through the above-describedconfiguration, a dark count rate (DCR) of the photoelectric conversionelement 102 can be suppressed.

One pixel 101 is isolated from another pixel 101 by a pixel isolationpart 324 having a trench structure, and the P-type fifth semiconductorregion 315 formed in the periphery thereof isolates one photoelectricconversion element 102 from another photoelectric conversion element 102adjacent thereto with a potential barrier. Because the photoelectricconversion elements 102 are isolated from one another by the potentialof the fifth semiconductor region 315, demarcation provided by a pixelisolation structure such as the pixel isolation part 324 having a trenchstructure is not essential. Further, when the pixel isolation part 324is to be arranged, a depth and a position thereof are not limited to theconfiguration illustrated in FIG. 6 . The pixel isolation part 324 maybe a deep trench isolation (DTI) which penetrates through thesemiconductor layer 301, or may be a DTI which does not penetrate thesemiconductor layer 301. Furthermore, a metal may be embedded in the DTIfor the sake of improving the light-shielding capability. The pixelisolation part 324 may be arranged to surround the entire circumferenceof the photoelectric conversion element 102 in the planar view, or maybe arranged on only side portions of the photoelectric conversionelement 102 opposite to each other.

A distance from a pixel isolation part 324 to one pixel 101 adjacentthereto, or a distance from one pixel isolation part 324 to anotherpixel isolation part 324 of a pixel 101 arranged at a closest position,can be regarded as a size of one photoelectric conversion element 102.When a size of one photoelectric conversion element 102 is L, a distanced from the light incident plane to the avalanche multiplication regionsatisfies a relational expression L√2/4<d<L×√2. In a case where a sizeand a depth of the photoelectric conversion element 102 satisfy theabove relational expression, the intensity of the electric field in adepth direction and the intensity of the electric field in an in-planedirection are substantially the same in a vicinity of the firstsemiconductor region 311. Occurrence of timing jitter can be reducedbecause variation in time required for electric charge collection can besuppressed.

Further, a pinning film 321, an interlayer film 322, and a micro-lens323 are formed on a side of the light incident plane of thesemiconductor layer 301. A filter layer (not illustrated) may also bearranged on the light incident plane side thereof. Various types ofoptical filters, e.g., a color filter, an infrared cut filter, and ablack-and-white filter, can be used for the filter layer. Ared-green-blur (RGB) color filter or a red-green-blue-white (RGBW) colorfilter can be used as the color filter.

Further, the photoelectric conversion apparatus 100 according to thepresent exemplary embodiment includes an antireflection film 326 and alight-shielding part 328 having an opening 327 arranged in a regionbetween the semiconductor layer 301 and the interlayer film 322.

A refractive index of the antireflection film 326 is lower than aneffective refractive index of the concavo-convex structure 325. Herein,the effective refractive index refers to a substantial refractive indexof the entire concavo-convex structure 325 configured of a base in whichthe trenches are formed and members embedded in the trenches. Forexample, in a case where the semiconductor layer 301 consists of silicon(Si) having a refractive index of 4, and the interlayer film 322consists of silicon monoxide (SiO) having a refractive index of 1.5, theeffective refractive index of the concavo-convex structure 325 is 2.8 to3.8. For example, the antireflection film 326 consists of tantalumpentoxide (Ta₂O₅) having a refractive index of around 2. By arrangingthe antireflection film 326 in a region between the semiconductor layer301 and the interlayer film 322, the refractive index is changedmoderately in the region from the semiconductor layer 301 to theinterlayer film 322. With this configuration, light of avalanche lightemission is prevented from being reflected on a rear surface of thesemiconductor layer 301, and occurrence of crosstalk caused by the lightof avalanche light emission can be reduced.

The opening 327 is arranged to enclose the first semiconductor region311 in a planar view viewed from a direction perpendicular to the lightincident plane. By arranging the light-shielding part 328 between thepixels 101, occurrence of crosstalk caused when the light of avalanchelight emission generated in one pixel 101 travels to the outside of theone pixel 101 and enters another pixel 101 adjacent thereto can bereduced.

With this configuration, a light path length greater than the thicknessof the semiconductor layer 301 can be secured by making incident lightscatter within the pixel 101, so that photoelectric conversion of lighthaving a longer wavelength can be executed, and light of avalanche lightemission described below can be efficiently released to the outside ofthe semiconductor layer 301.

FIG. 7 is a diagram illustrating a top plan view of the two pixels 101included in the photoelectric conversion apparatus 100 according to thepresent exemplary embodiment, taken along a dashed line A in FIG. 6 .The concavo-convex structure 325 is arranged on each of the pixels 101demarcated by the pixel isolation part 324. The micro-lens 323 isarranged along the pixel isolation part 324, and the concavo-convexstructure 325 and the fourth semiconductor region 314 are arranged tooverlap with each other.

FIG. 8 is an enlarged cross-sectional view taken along a dashed line Bin FIG. 7 , which illustrates two trench structures arranged in a regionwhere a first trench portion intersects with a second trench portion.The first trench portion refers to a trench portion extending in a firstdirection as an in-plane direction of the light incident plane (firstplane), and the second trench portion refers to a trench portionextending in a second direction intersecting with the first direction,from among the trench portions for constituting the concavo-convexstructure 325. Hereinafter, a portion of one trench portion extending inthe first or the second direction, where the one trench portion does notintersect with another trench portion, is called a line portion, and aportion where the one trench portion intersects with another trenchportion is called a cross portion.

The trench structure which forms the trench portions contains a materialdifferent from the material of the third semiconductor region 313. Forexample, in a case where the third semiconductor region 313 containssilicon, a member which mainly constitutes the trench structure is asilicon oxide film or a silicon nitride film, although the trenchstructure may include a metallic material or an organic material.

For example, a trench portion is formed with a depth of 0.1 μm to 0.6 μmfrom the surface of the semiconductor layer 301. In order tosufficiently increase a degree of diffraction of incident light, it ispreferable that a depth of the trench portion be greater than a widththereof. Herein, a width of the trench portion is a width from aninterfacial surface between the pinning film 321 and the thirdsemiconductor region 313 and an interfacial surface between the pinningfilm 321 and the third semiconductor region 313 on a plane passingthrough a gravity center portion of a cross-sectional plane of thetrench portion, and a depth of the trench portion is a depth from thelight incident plane to a bottom of the trench portion.

The trench portions which constitute the concavo-convex structure 325 inFIG. 8 are filled with filler members 332. For example, a silicon oxidefilm or a silicon nitride film is used as the filler member 332 when thethird semiconductor region 313 contains silicon. However, a metallicmaterial or an organic material may also be used as the filler member332. Airgaps 331 are formed in the interior of the filler member 332 inorder to increase a degree of change of refractive index at theconcavo-convex structure 325. The filler member 332 fills up the trenchportions of the concavo-convex structure 325 and covers the pinning film321 arranged in the interior of the trench portions.

Herein, each of the airgaps 331 is formed and located at a depthtwo-thirds the depth of the trench portion of the concavo-convexstructure 325 from the upper edge of the pinning film 321, so that theairgap 331 does not make contact with the bottom of the trenchstructure. If the airgap 331 reaches the bottom of the trench portion, arefractive index remains unchanged between the airgap 331 and the fillermember 332, and reflection at the bottom of the trench portion isincreased to cause lowering of sensitivity. Therefore, the airgap 331 isformed in the above-described state in order to prevent lowering ofsensitivity. In the example illustrated in FIG. 8 , the upper endportion of the airgap 331 conforms to the surface of the pinning film321.

FIG. 9 is a top plan view of the concavo-convex structure 325, whichillustrates positions where the airgaps 331 are generated in theconcavo-convex structure 325. In a case where the concavo-convexstructure 325 is arranged in a grid-like state as illustrated in FIG. 7, the airgaps 331 are generated at intersection points (cross portions)of the trench portions which form the concavo-convex structure 325.

Hereinafter, a forming method of the trench portion will be described.First, a trench portion is formed in the third semiconductor region 313of the semiconductor layer 301 by etching.

Thereafter, a pinning film 321 is formed on a surface of the thirdsemiconductor region 313 and in an interior of the trench portionthrough a method such as a chemical vapor deposition (CVD) method.

The filler member 332 is further embedded in the interior of the trenchportion covered by the pinning film 321. For example, the filler member332 is embedded therein through a chemical vapor deposition (CVD)method. A CVD method such as a thermal CVD method, a plasma-enhanced CVDmethod, or a low-pressure CVD method can be used. Further, the interiorcan be filled through a method such as a sol-gel method. At this time,by optimizing a film deposition condition of the CVD, a film depositionspeed in a corner part can be increased and faster than in a flat part.By closing the corner part earlier than the flat part, the airgap 331 isformed in the interior of the trench portion.

In the concavo-convex structure 325 configured of trench portionsarranged in a grid-like state, in a case where a line width of a lineportion is fixed, and the line portion orthogonally intersects withanother line portion at a cross portion, a line width of the crossportion in a diagonal direction is √2 times as large as a line width ofthe line portion in an opposite side direction. Therefore, when a trenchportion is filled with the filler member 332, an interior of the lineportion is closed before an interior of the cross portion is closed.Although a corner part of the line portion is closed earlier than a flatpart thereof, the entire line portion is filled with the filler member332 before the cross portion is closed because gas is supplied from anunclosed part of the cross portion. Therefore, a large airgap 331 formedin the cross portion is not formed in the line portion.

In a case where the airgap 331 is uniformly and continuously formed inthe entire trench portions of the concavo-convex structure 325, incidentlight is considerably diffracted in a specific direction because ofsymmetry of a refractive index change of the airgap 331. Therefore, anincrease amount of the optical path length is limited, so thatconsiderable optical color mixture is likely to occur in the adjacentpixels 101. As illustrated in FIG. 9 , in a case where airgaps 331 areformed only in the intersection points of the trench portions of theconcavo-convex structure 325, the light path length can be increasedbecause incident light is also diffracted in an oblique directionconsiderably. With this configuration, an effect of improving thesensitivity to near-infrared light can be increased. An effect ofreducing the optical color mixture can also be acquired because an angleof light incident on adjacent pixels 101 becomes greater.

In addition, the trench portions which form the concavo-convex structure325 and the trench portions which form the pixel isolation part 324 canbe filled in the same processing. In this case, side walls of the trenchportions for forming the concavo-convex structure 325 and side walls ofthe trench portions for forming the pixel isolation part 324 haveequivalent impurity concentrations. Hereinafter, a difference betweenstructures of the trench portions for forming the concavo-convexstructure 325 and the trench portions for forming the pixel isolationpart 324 will be described.

FIG. 10A is a diagram illustrating an enlarged cross-sectional view ofthe concavo-convex structure 325 and the pixel isolation part 324 takenalong a dashed line B in FIG. 7 . FIG. 10B is a diagram illustrating anenlarged cross-sectional view of the concavo-convex structure 325 andthe pixel isolation part 324 taken along a dashed line C in FIG. 7 .

The pixel isolation part 324 is a trench structure of a depthpenetrating through the third semiconductor region 313, and the pixelisolation part 324 and the concavo-convex structure 325 are filled withthe same filler member 332 simultaneously. As described above, thefiller member 332 may be a silicon oxide film or a silicon nitride film,or may be a metallic material or an organic material. It is possible tosimplify the processing by filling the pixel isolation part 324 and theconcavo-convex structure 325 in the same processing.

An airgap 333 is formed in the interior of the filler member 332embedded in the pixel isolation part 324. The airgap 333 is arranged inthe interior of the pixel isolation part 324 on both of thecross-sectional plane (dashed line B) corresponding to the cross portionof the concavo-convex structure 325 and the cross-sectional plane(dashed line C) corresponding to the line portion thereof. On the otherhand, as described above, the airgap 331 arranged in the concavo-convexstructure 325 is formed on the cross-sectional plane (dashed line B)corresponding to the cross portion of the concavo-convex structure 325,and is not formed on the cross-sectional plane (dashed line C)corresponding to the line portion thereof. This is because the pixelisolation part 324 formed as an isolation structure for preventing lightfrom leaking to the adjacent pixel 101 has a line width wider than thatof the concavo-convex structure 325, and the airgap 333 is easily formedin the pixel isolation part 324. In other words, a width of the pixelisolation part 324 in a third direction as an in-plane direction of thefirst plane is wider than a width of a trench portion for forming theconcavo-convex structure 325 in the third direction. Because lighttransmissivity of the airgap is lower than that of the filler member332, an effect of preventing leakage of light to the adjacent pixel 101is improved by forming the airgap in the interior of the isolationstructure.

Further, an upper end of the airgap 333 (an end portion on a side of thefirst plane) is located at a position deeper than a position of an upperend of the airgap 331 from the light incident plane, and a lower end ofthe airgap 333 (an end portion on a side of the second plane) is locatedat a position deeper than a position of a lower end of the airgap 331from the light incident plane. In other words, a shortest distance fromthe first plane (light incident plane) to the end portion of the airgap333 on a side of the second plane (i.e., plane opposite to the lightincident plane), arranged in the interior of the pixel isolation part324, is greater than a shortest distance from the light incident planeto the end portion of the airgap 331 on a side of the plane opposite tothe light incident plane, arranged in the interior of the concavo-convexstructure 325. As described above, because the pixel isolation part 324has a wider line width, a larger amount of filler members 332 arenecessary in order to fill the interior of the trench portion. Byfilling the interior of the trench portion in a state where the airgap333 is formed in a lower part thereof, the interior of the trenchportion can be closed with a small amount of filler members 332.

In addition, the airgaps 331 and 333 can be formed at optional positionsdepending on a trench pattern, a tapered shape of the trench portion,and a filling method of the filler member 332.

A photoelectric conversion apparatus 100 according to a second exemplaryembodiment will be described with reference to FIG. 11 .

Descriptions common to the first exemplary embodiment are omitted, and aconfiguration different from that of the first exemplary embodiment ismainly described. In the present exemplary embodiment, the airgap 331 isalso formed in the line portion of the concavo-convex structure 325.

FIG. 11 is a plan view of the concavo-convex structure 325 arranged onone pixel 101 of the photoelectric conversion apparatus 100 according tothe present exemplary embodiment, which illustrates plan positions ofairgaps 331 formed in the concavo-convex structure 325 arranged in agrid-like state.

In the present exemplary embodiment, the airgaps 331 are arranged notonly in the cross portions but also in the line portions. A fillermember 332 is arranged in a region between the airgap 331 arranged inthe cross portion and the airgap 331 arranged in the line portion, sothat the airgap 331 in the cross portion and the airgap 331 in the lineportion are not formed continuously. By forming the airgap 331 in thecross portion and the airgap 331 in the line portion discontinuously, adegree of diffraction is increased because of a difference betweenrefractive indexes of the airgap 331 and the filler member 332, so thatan effect of improving the sensitivity to near-infrared light can beacquired.

A photoelectric conversion apparatus 100 according to a third exemplaryembodiment will be described with reference to FIG. 12 .

Descriptions common to the first exemplary embodiment are omitted, and aconfiguration different from that of the first exemplary embodiment ismainly described. In the present exemplary embodiment, the airgaps 331are formed in part of the line portions of the concavo-convex structure325.

FIG. 12 is a plan view of the concavo-convex structure 325 arranged onone pixel 101 of the photoelectric conversion apparatus 100 according tothe present exemplary embodiment, which illustrates plan positions ofairgaps 331 formed in the concavo-convex structure 325 arranged in agrid-like state. The airgaps 331 are formed in the cross portions andpart of the line portions of the concavo-convex structure 325. Theairgaps 331 are formed in the line portions located in a region close tothe central part of the pixel 101 on which a large amount of light isincident.

By increasing a line width of a trench portion for forming theconcavo-convex structure 325, an interior of the trench portion isslowly closed with the filler member 332, so that an airgap 331 isgenerated. Therefore, the airgap 331 can be formed in a desired positionby making a line width of the trench portion where the airgap 331 is tobe created wider than a line width of the trench portion where theairgap 331 is not created. For example, by making a line width of thetrench portion where the airgap 331 is to be created √2 times as largeas a line width of the trench portion where the airgap 331 is notcreated, the airgap 331 similar to the one formed in the cross portioncan be formed. As described above, by controlling the arrangement ofairgaps 331 formed in the concavo-convex structure 325, it is possibleto control the sensitivity and the optical color mixture depending onthe properties of the photoelectric conversion apparatus 100.

A photoelectric conversion system according to a fourth exemplaryembodiment will be described with reference to FIG. 13 . FIG. 13 is ablock diagram illustrating a schematic configuration of thephotoelectric conversion system according to the present exemplaryembodiment.

The photoelectric conversion apparatus 100 described in the first to thesixth exemplary embodiments can be applied to various photoelectricconversion systems. A digital still camera, a digital camcorder, amonitoring camera, a copying machine, a facsimile machine, a mobilephone, an in-vehicle camera, and an observation satellite are given asthe examples of the applicable photoelectric conversion system. Further,a camera module which includes an optical system such as a lens and animage capturing apparatus is also included in the photoelectricconversion system. FIG. 13 illustrates a block diagram of a digitalstill camera as one example.

The photoelectric conversion system illustrated in FIG. 13 includes animage capturing apparatus 1004 as one example of the photoelectricconversion apparatus 100 and a lens 1002 which forms an optical image ofan object on the image capturing apparatus 1004. The photoelectricconversion system further includes an aperture 1003 capable of changingan amount of light passing through the lens 1002 and a barrier 1001 forprotecting the lens 1002. The lens 1002 and the aperture 1003 functionas an optical system which condenses light to the image capturingapparatus 1004. The image capturing apparatus 1004 is the photoelectricconversion apparatus 100 according to any one of the above-describedexemplary embodiments, and the image capturing apparatus 1004 convertsan optical image formed by the lens 1002 into an electric signal.

The photoelectric conversion system further includes a signal processingunit or circuit 1007 which serves as an image generation unit togenerate an image by executing processing on a signal output from theimage capturing apparatus 1004. The signal processing unit 1007 executesvarious types of correction and compression as necessary, and outputsimage data. The signal processing unit 1007 may be formed on asemiconductor substrate on which the image capturing apparatus 1004 ismounted, or may be formed on a semiconductor substrate different fromthe semiconductor substrate where the image capturing apparatus 1004 ismounted.

The photoelectric conversion system further includes a memory unit 1010for temporarily storing image data and an external interface (I/F) unit1013 for communicating with an external computer. Furthermore, thephotoelectric conversion system includes a recording medium 1012 such asa semiconductor memory for recording and reading captured image data anda recording medium control interface (I/F) unit or circuit 1011 forrecording captured image data in the recording medium 1012 and readingcaptured image data from the recording medium 1012. In addition, therecording medium 1012 may be built into the photoelectric conversionsystem, or may be attachable to and detachable from the photoelectricconversion system.

Further, the photoelectric conversion system includes a generalcontrol/calculation unit or circuit 1009 which executes various types ofcalculation and control of the entire digital still camera, and a timinggeneration unit or circuit 1008 which outputs various timing signals tothe image capturing apparatus 1004 and the signal processing unit 1007.Herein, a timing signal may be input thereto from the outside.Therefore, the photoelectric conversion system may include at least theimage capturing apparatus 1004 and the signal processing unit 1007 forexecuting processing on a signal output from the image capturingapparatus 1004.

The image capturing apparatus 1004 outputs an imaging signal to thesignal processing unit 1007. The signal processing unit 1007 executespredetermined signal processing on the imaging signal output from theimage capturing apparatus 1004, and outputs image data. The signalprocessing unit 1007 generates an image by using the imaging signal.

As described above, according to the present exemplary embodiment, it ispossible to realize a photoelectric conversion system to which thephotoelectric conversion apparatus 100 (image capturing apparatus)according to any one of the above-described exemplary embodiments isapplied.

A photoelectric conversion system and a moving body according to a fifthexemplary embodiment will be described with reference to FIGS. 14A and14B. FIGS. 14A and 14B are diagrams illustrating configurations of thephotoelectric conversion system and the moving body according to thepresent exemplary embodiment.

FIG. 14A illustrates an example of the photoelectric conversion systemapplied to an in-vehicle camera. A photoelectric conversion system 2300includes an image capturing apparatus 2310. The image capturingapparatus 2310 is the photoelectric conversion apparatus 100 accordingto any one of the above-described exemplary embodiments. Thephotoelectric conversion system 2300 includes an image processing unitor circuit 2312 for executing image processing on a plurality of piecesof image data acquired by the image capturing apparatus 2310 and aparallax acquisition unit or circuit 2314 for calculating a parallax(i.e., a phase difference between parallax images) from a plurality ofpieces of image data acquired by the photoelectric conversion system2300. The photoelectric conversion system 2300 further includes adistance acquisition unit or circuit (distance measurement unit) 2316for calculating a distance to a target object based on the calculatedparallax, and a collision determination unit or circuit 2318 fordetermining a possibility of collision based on the calculated distance.Herein, the parallax acquisition unit 2314 and the distance acquisitionunit 2316 are examples of a distance information acquisition unit whichacquires distance information about a distance to a target object. Inother words, the distance information refers to information about aparallax, a defocus amount, and a distance to a target object. Thecollision determination unit 2318 may determine a possibility ofcollision by using any one of the pieces of distance information. Thedistance information acquisition unit may be configured of hardwareexclusively designed, or may be configured of a software module.

Further, the distance information acquisition unit may be configured ofa field programmable gate array (FPGA) or an application specificintegrated circuit (ASIC), or may be configured of a combination ofthese elements.

The photoelectric conversion system 2300 is connected to a vehicleinformation acquisition device 2320, and can acquire vehicle informationsuch as a vehicle speed, a yaw rate, and a rudder angle. Further, thephotoelectric conversion system 2300 is connected to a control ECU (ECU:electronic control unit) 2330. The control ECU 2330 is a control unitwhich outputs a control signal for generating braking power to thevehicle based on a determination result acquired by the collisiondetermination unit 2318. The photoelectric conversion system 2300 isalso connected to an alarming device 2340 which issues a warning to adriver based on a determination result acquired by the collisiondetermination unit 2318. For example, in a case where the collisiondetermination unit 2318 determines that a possibility of collision ishigh, the control ECU 2330 executes vehicle control to avoid a collisionor to reduce damages by applying a brake, releasing a gas pedal, orsuppressing an engine output. The alarming device 2340 issues a warningto the driver by making alarm sound, displaying alarming information ona display screen of a car navigation system, or producing vibrations ina seat belt or steering wheels.

In the present exemplary embodiment, peripheral views of the vehicle,e.g., a forward view and a backward view of the vehicle are captured bythe photoelectric conversion system 2300. FIG. 14B illustrates a statewhere a forward view (image capturing range 2350) of the vehicle iscaptured by the photoelectric conversion system 2300. The vehicleinformation acquisition device 2320 issues an instruction to thephotoelectric conversion system 2300 or the image capturing apparatus2310. Through the above-described configuration, it is possible tofurther improve the range finding accuracy.

In the above-described exemplary embodiment, although control processingfor preventing the vehicle from colliding with another vehicle has beendescribed as an example, the disclosure can also be applied to controlprocessing which enables the vehicle to be automatically driven whilefollowing another vehicle or control processing which enables thevehicle to be automatically driven without being drifted out of atraffic lane. Further, the photoelectric conversion system 2300 can beapplied not only to vehicles such as automobiles but also to movingbodies (moving apparatuses) such as a ship, an airplane, and anindustrial robot. In addition, the photoelectric conversion system 2300can be applied not only to the moving bodies but also to a device suchas an intelligent transportation system (ITS) which widely employs anobject recognition function.

A photoelectric conversion system according to a sixth exemplaryembodiment will be described with reference to FIG. 15 . FIG. 15 is ablock diagram illustrating a configuration example of a distance imagesensor as an example of the photoelectric conversion system according tothe present exemplary embodiment.

As illustrated in FIG. 15 , a distance image sensor 401 includes anoptical system 402, a photoelectric conversion apparatus 403, an imageprocessing circuit 404, a monitor 405, and a memory 406. The distanceimage sensor 401 can acquire a distance image according to a distance toan object by receiving light emitted from a light source device 411 tothe object and reflected on a surface of the object (i.e., modulatedlight or pulsed light).

The optical system 402 is configured of one or a plurality of lenses.The optical system 402 introduces image light (incident light) from anobject to the photoelectric conversion apparatus 403, and forms an imageon a light receiving plane (sensor part) of the photoelectric conversionapparatus 403.

The photoelectric conversion apparatus 100 according to theabove-described exemplary embodiment is applied to the photoelectricconversion apparatus 403, and a distance signal indicating a distance,which can be acquired from a light receiving signal output from thephotoelectric conversion apparatus 403, is supplied to the imageprocessing circuit 404.

Based on the distance signal supplied from the photoelectric conversionapparatus 403, the image processing circuit 404 executes imageprocessing to create a distance image. The distance image (image data)acquired from the image processing is supplied to and displayed on themonitor 405, or supplied to and stored (recorded) in the memory 406.

According to the distance image sensor 401 configured as the above,properties of the pixels are improved by applying the above-describedphotoelectric conversion apparatus 100. Therefore, for example, it ispossible to acquire a distance image more accurately.

A photoelectric conversion system according to a seventh exemplaryembodiment will be described with reference to FIG. 16 . FIG. 16 is adiagram illustrating an example of a schematic configuration of anendoscopic operation system as an example of a photoelectric conversionsystem according to the present exemplary embodiment.

FIG. 16 illustrates a state where an operator (doctor) 1131 performs anoperation on a patient 1132 lying on a patient bed 1133 by using anendoscopic operation system 1150. As illustrated in FIG. 16 , theendoscopic operation system 1150 is configured of an endoscope 1100, asurgical tool 1110, and a cart 1134 on which various devices forexecuting the endoscopic operation are mounted.

The endoscope 1100 is configured of a lens tube 1101 and a camera head1102 connected to a base end section of the lens tube 1101, and aleading end portion of the lens tube 1101 having a predetermined lengthis inserted to a coelom of the patient 1132. In FIG. 16 , the endoscope1100 is illustrated as a so-called rigid endoscope having the rigid lenstube 1101. However, the endoscope 1100 can be a so-called flexibleendoscope having a flexible lens tube.

A leading end of the lens tube 1101 includes an opening portion on whichan objective lens is mounted. A light source device 1203 is connected tothe endoscope 1100, so that light generated by the light source device1203 is introduced to the leading end of the lens tube 1101 by a lightguide arranged to extend through the inner portion of the lens tube 1101and emitted to an observation target inside the coelom of the patient1132 via the objective lens. In addition, the endoscope 1100 can be aforward viewing endoscope, an oblique viewing endoscope, or a sideviewing endoscope.

An optical system and a photoelectric conversion apparatus are arrangedin the interior of the camera head 1102, and reflection light(observation light) reflected from the observation target is condensedto the photoelectric conversion apparatus through the optical system.The photoelectric conversion apparatus executes photoelectric conversionon the observation light and generates an electric signal correspondingto the observation light, i.e., an image signal corresponding to anobservation image. The photoelectric conversion apparatus 100 accordingto the above-described exemplary embodiment can be used as thephotoelectric conversion apparatus. The image signal is transmitted to acamera control unit (CCU) or circuit 1135 in a form of RAW data.

The CCU 1135 is configured of a central processing unit (CPU) and agraphics processing unit (GPU), and comprehensively controls theoperation of the endoscope 1100 and a display device 1136. Further, theCCU 1135 receives an image signal from the camera head 1102 and executesvarious types of image processing such as development processing(de-mosaic processing) on the image signal in order to display an imagebased on the image signal.

The display device 1136 is controlled by the CCU 1135 to display animage based on the image signal on which the image processing isexecuted by the CCU 1135.

For example, the light source device 1203 is configured of a lightsource such as a light emitting diode (LED), and supplies irradiationlight to the endoscope 1100 when an operative field image is to becaptured.

An input device 1137 is an input interface of the endoscopic operationsystem 1150. A user can input various types of information andinstructions to the endoscopic operation system 1150 via the inputdevice 1137.

A surgical tool control device 1138 executes driving control of anenergy surgical tool 1112 used for cauterizing and incising livingtissues or sealing a blood vessel.

For example, the light source device 1203 can be configured of an LED, alaser light source, or a white light source configured of a combinationof these elements, and supplies irradiation light to the endoscope 1100when an operative field image is to be captured. In a case where thewhite light source is configured of a combination of RGB laser lightsources, output intensities and output timings of respective colors(wavelengths) can be controlled with high accuracy. Therefore, a whitebalance of the captured image can be adjusted by the light source device1203. Further, in this case, the observation target is irradiated withlaser light beams emitted from the RGB laser light sources in a timedivision manner, and image sensors of the camera head 1102 arecontrolled and driven in synchronization with the irradiation timing. Inthis way, images corresponding to respective RGB laser beams can becaptured in the time division manner. Through the above-describedmethod, it is possible to acquire color images without arranging colorfilters on the image sensors.

Further, the light source device 1203 may be controlled and driven inorder to change intensity of output light at every specified time. Byacquiring and combining images in a time division manner by executingdriving control of the image sensors of the camera head 1102 insynchronization with the timing of changing light intensity, theendoscopic operation system 1150 can generate so-called wide dynamicrange image data without including underexposed or overexposed data.

The light source device 1203 may be configured to supply light of apredetermined wavelength band for special light observation. Forexample, the special light observation is executed by making use ofwavelength dependence of light absorption of the living tissues.Specifically, specific tissues such as blood vessels on a mucousmembrane surface are captured with high contrast by irradiating thetissues with light having a wavelength band narrower than a wavelengthband of irradiation light (i.e., white light) used for normalobservation.

Alternatively, the special light observation such as fluorescenceobservation for acquiring an image by generating fluorescence in livingtissues by irradiating the living tissues with excitation light may beexecuted. In the fluorescence observation, fluorescence generated fromliving tissues can be observed by irradiating the living tissues withexcitation light. Further, a fluorescent image can also be acquired bylocally injecting test reagent such as indocyanine green (ICG) intoliving tissues and irradiating the living tissues with excitation lightcorresponding to a fluorescence wavelength of that test reagent. Thelight source device 1203 may be configured to supply narrow-band lightand/or excitation light for the above-described special lightobservation.

A photoelectric conversion system according to an eighth exemplaryembodiment will be described with reference to FIGS. 17A and 17B. FIG.17A is a diagram illustrating a pair of eyeglasses 1600 (a pair ofsmart-glasses) as an example of the photoelectric conversion systemaccording to the present exemplary embodiment. The pair of eyeglasses1600 includes a photoelectric conversion apparatus 1602. Thephotoelectric conversion apparatus 1602 is the photoelectric conversionapparatus 100 according to the above-described exemplary embodiment.Further, a display device including a light emitting device such as anorganic light emitting diode (OLED) or an LED may be mounted on a rearface of each of lenses 1601. One or more photoelectric conversionapparatus 1602 may be mounted thereon. Further, a plurality of types ofphotoelectric conversion apparatuses may be used in combination. Amounting position of the photoelectric conversion apparatus 1602 is notlimited to the position illustrated in FIG. 17A.

The pair of eyeglasses 1600 further includes a control device 1603. Thecontrol device 1603 functions as a power source for supplying power tothe photoelectric conversion apparatus 1602 and the above-describeddisplay device. The control device 1603 further controls the operationsof the photoelectric conversion apparatus 1602 and the display device.An optical system which condenses light to the photoelectric conversionapparatus 1602 is formed on the lens 1601.

FIG. 17B illustrates a pair of eyeglasses 1610 (a pair of smart-glasses)according to one application example. The pair of eyeglasses 1610includes a control device 1612, and a photoelectric conversion apparatuscorresponding to the photoelectric conversion apparatus 1602 and adisplay device are mounted on the control device 1612. An optical systemfor projecting light emitted from the photoelectric conversion apparatusand the display device included in the control device 1612 is formed oneach of lenses 1611, so that images are projected thereon. The controldevice 1612 functions as a power source for supplying power to thephotoelectric conversion apparatus and the display device, and alsocontrols the operation of the photoelectric conversion apparatus and thedisplay device. The control device 1612 may include a line-of-sightdetection unit for detecting a line-of-sight of the user. Infrared lightmay be used for detecting the line-of-sight. An infrared light emittingunit emits infrared light to the eyeball of the user who is gazing at adisplay image. An image capturing unit having a light receiving elementdetects the emitted infrared light reflected on the eyeball, so thatcaptured image of the eyeball can be acquired. It is possible tosuppress lowering of image quality by arranging a reduction unit whichreduces light emitted to the display portion from the infrared lightemitting unit in a planar view.

The line-of-sight of the user gazing at the display image can bedetected from the captured image of the eyeball acquired from imagecapturing using infrared light. An optional known method can be employedfor line-of-sight detection using the captured image of the eyeball. Forexample, it is possible to employ a method of detecting a line-of-sightbased on a Purkinje image acquired from irradiation light reflected onthe cornea.

More specifically, line-of-sight detection processing using apupil-corneal reflection method is executed. In the pupil-cornealreflection method, a line-of-sight vector which expresses theorientation (rotation angle) of the eyeball is calculated based on apupil image and a Purkinje image included in the captured image of theeyeball, and a user's line-of-sight is detected from the calculatedline-of-sight vector.

The display device according to the present exemplary embodiment mayinclude a photoelectric conversion apparatus having a light receivingelement, and a display image displayed on the display device may becontrolled based on the user's line-of-sight information received fromthe photoelectric conversion apparatus.

Specifically, based on the line-of-sight information, the display devicedetermines a first field-of-view region where the user is gazing at anda second field-of-view region different from the first field-of-viewregion. The first and second field-of-view regions may be determined bythe control device of the display device, or the display device mayreceive the first and the second field-of-view regions determined by anexternal control device. In the display area of the display device, adisplay resolution of the first field-of-view region may be controlledto be higher than that of the second field-of-view region. In otherwords, the second field-of-view region may be displayed in a resolutionlower than that of the first field-of-view region.

Further, the display area may have a first display area and a seconddisplay area different from the first display area, and an area ofhigher priority may be determined from the first and the second displayareas based on the line-of-sight information. The first and the seconddisplay areas may be determined by the control device of the displaydevice, or the display device may receive the first and the seconddisplay areas determined by an external control device. The resolutionof the area of higher priority may be controlled to be higher than theresolution of the area different from the area of higher priority. Inother words, resolution of the area of relatively low priority may bereduced.

In addition, an artificial intelligence (AI) program may be used fordetermining the first field-of-view region and the area of higherpriority. The AI program may be a model configured to estimate an angleof the line-of-sight and a distance to an object to which theline-of-sight is directed from an image of the eyeball by using an imageof the eyeball and the actual line-of-sight direction of the eyeball inthe image as training data. The AI program may be included in thedisplay device, the photoelectric conversion apparatus, or an externaldevice. In a case where the AI program is included in the externaldevice, information is transmitted to the display device throughcommunication.

In a case where display control is executed based on line-of-sightdetection, the present exemplary embodiment can favorably be applied toa pair of smart-glasses which further includes a photoelectricconversion apparatus for capturing an outside view. The pair ofsmart-glasses can display information about the captured outside view inreal time.

<Variation of Exemplary Embodiments>

The disclosure is not limited to the above-described exemplaryembodiments, and various changes and modifications are possible.

For example, an exemplary embodiment in which part of the configurationsaccording to any one of the above-described exemplary embodiments isadded to another exemplary embodiment or replaced with part of theconfigurations according to another exemplary embodiment is alsoincluded in the exemplary embodiments.

Further, the photoelectric conversion systems described in the fourthand fifth exemplary embodiments are merely examples of the photoelectricconversion system to which the photoelectric conversion apparatus can beapplied, and a configuration of the photoelectric conversion system, towhich the photoelectric conversion apparatus according to the disclosurecan be applied, is not limited to the configurations illustrated inFIGS. 13, 14A, and 14B. The same can also be said for the TOF systemdescribed in the sixth exemplary embodiment, the endoscopic operationsystem described in the seventh exemplary embodiment, and the pair ofsmart-glasses described in the eighth exemplary embodiment.

In addition, the above-described exemplary embodiments are merely theexamples embodying the disclosure, and shall not be construed aslimiting the technical range of the disclosure. In other words, thedisclosure can be realized in diverse ways without departing from thetechnical spirit or main features of the disclosure.

According to an aspect of the embodiments, it is possible to provide aphotoelectric conversion system capable of reducing optical colormixture of a photoelectric conversion apparatus.

While the disclosure has been described with reference to exemplaryembodiments, it is to be understood that the disclosure is not limitedto the disclosed exemplary embodiments. The scope of the followingclaims is to be accorded the broadest interpretation so as to encompassall such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2022-040248, filed Mar. 15, 2022, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A photoelectric conversion apparatus comprising:a plurality of photoelectric conversion circuits configured to bearranged in a semiconductor layer having a first plane and a secondplane opposite to the first plane, wherein the plurality ofphotoelectric conversion circuits is individually isolated by anisolation structure, wherein the semiconductor layer includes aplurality of trench portions arranged on the first plane of each of thephotoelectric conversion circuits demarcated by the isolation structure,wherein the plurality of trench portions is configured of a first trenchportion extending in a first direction as an in-plane direction of thefirst plane and a second trench portion extending in a second directionas an in-plane direction of the first plane intersecting with the firstdirection, and wherein a filler member and an airgap are arranged in aninterior of a trench portion at a position where the first trenchportion and the second trench portion intersect with each other.
 2. Thephotoelectric conversion apparatus according to claim 1, wherein afiller member and an airgap are arranged in an interior of the isolationstructure.
 3. A photoelectric conversion apparatus comprising: aplurality of photoelectric conversion circuits configured to be arrangedin a semiconductor layer having a first plane and a second planeopposite to the first plane, wherein the plurality of photoelectricconversion circuits is individually isolated by an isolation structure,wherein the semiconductor layer includes a plurality of trench portionsarranged on the first plane, and wherein a filler member and airgaps arearranged in interiors of the plurality of trench portions and theisolation structure.
 4. The photoelectric conversion apparatus accordingto claim 3, wherein the airgap is arranged in an interior of a trenchportion at a position where a first trench portion extending in a firstdirection as an in-plane direction of the first plane and a secondtrench portion extending in a second direction as an in-plane directionof the first plane intersecting with the first direction intersect witheach other.
 5. The photoelectric conversion apparatus according to claim2, wherein a shortest distance from the first plane to an end portion ofan airgap on a side of the second plane, arranged in the interior of theisolation structure, is greater than a shortest distance from the firstplane to an end portion of an airgap on the side of the second plane,arranged in the interior of the trench portion.
 6. The photoelectricconversion apparatus according to claim 2, wherein a length of an airgapfrom one end portion on a side of the first plane to another end portionon a side of the second plane, arranged in the interior of the trenchportion, is shorter than a length of an airgap from one end portion onthe side of the first plane to another end portion on the side of thesecond plane, arranged in the interior of the isolation structure. 7.The photoelectric conversion apparatus according to claim 2, wherein awidth of the isolation structure in a third direction as an in-planedirection of the first plane is larger than a width of the trenchportion in the third direction.
 8. The photoelectric conversionapparatus according to claim 1, wherein the filler member is arranged ina region between an end portion of the trench portion on a side of thesecond plane and an end portion of the airgap on the side of the secondplane arranged in the interior of the trench portion.
 9. Thephotoelectric conversion apparatus according to claim 1, wherein an endportion of the airgap on a side of the first plane arranged in theinterior of the trench portion conforms to the first plane.
 10. Thephotoelectric conversion apparatus according to claim 1, wherein aregion between an airgap arranged at a position where the first trenchportion and the second trench portion intersect with each other and anairgap arranged in the first trench portion is filled with the fillermember.
 11. The photoelectric conversion apparatus according to claim 1,wherein the trench portion has a trench structure.
 12. The photoelectricconversion apparatus according to claim 1, wherein the filler member isan oxide film or a nitride film.
 13. A photoelectric conversion systemincluding the photoelectric conversion apparatus according to claim 1,comprising: a light emitting circuit configured to emit light detectedby the photoelectric conversion apparatus; and a calculation circuitconfigured to calculate a distance by using a digital signal retained bythe photoelectric conversion apparatus.
 14. A moving body comprising:the photoelectric conversion apparatus according to claim 1; a distanceinformation acquisition circuit configured to acquire distanceinformation about a distance to a target object from a parallax imagebased on a signal from the photoelectric conversion apparatus; and acontrol circuit configured to control the moving body based on thedistance information.
 15. The photoelectric conversion apparatusaccording to claim 3, wherein a shortest distance from the first planeto an end portion of an airgap on a side of the second plane, arrangedin the interior of the isolation structure, is greater than a shortestdistance from the first plane to an end portion of an airgap on the sideof the second plane, arranged in the interior of the trench portion. 16.The photoelectric conversion apparatus according to claim 3, wherein alength of an airgap from one end portion on a side of the first plane toanother end portion on a side of the second plane, arranged in theinterior of the trench portion, is shorter than a length of an airgapfrom one end portion on the side of the first plane to another endportion on the side of the second plane, arranged in the interior of theisolation structure.
 17. The photoelectric conversion apparatusaccording to claim 3, wherein a width of the isolation structure in athird direction as an in-plane direction of the first plane is largerthan a width of the trench portion in the third direction.
 18. Thephotoelectric conversion apparatus according to claim 3, wherein an endportion of the airgap on a side of the first plane arranged in theinterior of the trench portion conforms to the first plane.
 19. Aphotoelectric conversion system including the photoelectric conversionapparatus according to claim 3, comprising: a light emitting circuitconfigured to emit light detected by the photoelectric conversionapparatus; and a calculation circuit configured to calculate a distanceby using a digital signal retained by the photoelectric conversionapparatus.
 20. A moving body comprising: the photoelectric conversionapparatus according to claim 3; a distance information acquisitioncircuit configured to acquire distance information about a distance to atarget object from a parallax image based on a signal from thephotoelectric conversion apparatus; and a control circuit configured tocontrol the moving body based on the distance information.